| HURRICANE FRED DISCUSSION NUMBER 8 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL072009 1100 AM AST WED SEP 09 2009 FRED HAS CONTINUED TO RAPIDLY INTENSIFY THIS MORNING AND IS NOW A MAJOR HURRICANE. SATELLITE IMAGES SHOW THAT THE EYE HAS BECOME DISTINCT ON BOTH VISIBLE AND INFRARED CHANNELS AND REMAINS EMBEDDED WITHIN A COLD CENTRAL DENSE OVERCAST. THE LATEST DVORAK ESTIMATES FROM TAFB/SAB ARE 102 KT...WITH OBJECTIVE T-NUMBERS NEAR 115 KT. THE INITIAL INTENSITY IS RAISED TO 105 KT...MAKING FRED THE SECOND MAJOR HURRICANE OF THE SEASON. ADDITIONAL STRENGTHENING IS POSSIBLE TODAY BEFORE INCREASING SHEAR AND SLIGHTLY COOLER WATERS CAUSE FRED TO WEAKEN TOMORROW. THEREAFTER...THE HURRICANE WILL BE MOVING OVER MARGINAL SSTS COOLER AND INTO A DRIER MID-LEVEL AIRMASS...WHICH SHOULD ENHANCE THE WEAKENING EFFECTS OF THE EXPECTED STRONG SHEAR. THE LATEST NHC FORECAST IS CLOSE TO A BLEND OF THE SHIPS MODEL AND THE PREVIOUS FORECAST. THE GFDL AND HWRF MODELS...WHICH APPEAR TO BE LESS SENSITIVE TO INCREASED SHEAR...DO NOT WEAKEN FRED NEARLY AS MUCH AS THE OFFICIAL FORECAST AT DAYS 4 AND 5. THE MOTION CONTINUES TO BEND GRADUALLY TO THE RIGHT AND IS NOW ABOUT 305/11. THERE IS NO CHANGE TO THE FORECAST REASONING AS MOST GUIDANCE IS WELL-CLUSTERED ON A GRADUAL TURN TOWARD THE NORTH AND NORTHEAST DUE TO A MID- TO UPPER-LEVEL TROUGH OVER THE CENTRAL ATLANTIC. IN ABOUT 48 HOURS...ALL GUIDANCE SIGNIFICANTLY DECELERATES FRED AS THE HURRICANE BECOMES CAUGHT IN LIGHT STEERING CURRENTS. MOST OF THE GLOBAL MODELS REBUILD THE RIDGE TO THE NORTH OF FRED BY THE END OF FORECAST PERIOD...WHICH WOULD CAUSE THE CYCLONE TO MOVE MORE TO THE NORTHWEST. THE OFFICIAL FORECAST IS SLIGHTLY EAST OF THE MODEL CONSENSUS INITIALLY...THEN ENDS UP SOMEWHAT TO THE WEST IN THE ANTICIPATION THAT A WEAKER SYSTEM WOULD TAKE A MORE WESTWARD PATH. THE TWO BIGGEST OUTLIERS TO THIS FORECAST ARE THE GFDL AND HWRF...WHICH TAKE FRED FARTHER NORTH THAN MOST OF THE OTHER MODELS...PROBABLY BECAUSE THEY KEEP IT AS A DEEP CYCLONE FOR TOO LONG. IT IS QUITE UNUSUAL TO HAVE SUCH A POWERFUL SYSTEM SO FAR EAST IN THE BASIN AND FRED IS ONLY THE THIRD MAJOR HURRICANE NOTED EAST OF 35W IN THE TROPICAL ATLANTIC OCEAN...AND THE STRONGEST HURRICANE SO FAR SOUTH AND EAST IN OUR DATA RECORD. THIS TYPE OF SYSTEM... HOWEVER...WOULD HAVE BEEN VERY DIFFICULT TO ACCURATELY OBSERVE BEFORE SATELLITE PICTURES BEGAN IN THE 1960S. FORECAST POSITIONS AND MAX WINDS INITIAL 09/1500Z 13.9N 32.4W 105 KT 12HR VT 10/0000Z 14.9N 33.5W 110 KT 24HR VT 10/1200Z 16.2N 34.3W 105 KT 36HR VT 11/0000Z 17.2N 34.7W 90 KT 48HR VT 11/1200Z 17.7N 34.6W 80 KT 72HR VT 12/1200Z 18.7N 34.0W 60 KT 96HR VT 13/1200Z 20.5N 34.2W 45 KT 120HR VT 14/1200Z 23.5N 36.0W 30 KT $$ FORECASTER BLAKE |